External and implantable coils for auditory prostheses

ABSTRACT

Certain medical devices, such as auditory prostheses, have an implantable portion and an external portion. The implantable portion and external portion each include a transmission/receiver coil that communicates signals between the two portions. The implanted coil is implanted about the ear canal while the external coil is disposed about the pinna or in the ear canal itself. The proximity of the two coils allows for signal transmission between the implantable and external portions.

BACKGROUND

Hearing loss, which can be due to many different causes, is generally oftwo types: conductive and sensorineural. Sensorineural hearing loss isdue to the absence or destruction of the hair cells in the cochlea thattransduce sound signals into nerve impulses. Various hearing prosthesesare commercially available to provide individuals suffering fromsensorineural hearing loss with the ability to perceive sound. Forexample, cochlear implants use an electrode array implanted in thecochlea of a recipient (i.e., the inner ear of the recipient) to bypassthe mechanisms of the middle and outer ear. More specifically, anelectrical stimulus is provided via the electrode array to the auditorynerve, thereby causing a hearing percept.

Conductive hearing loss occurs when the normal mechanical pathways thatprovide sound to hair cells in the cochlea are impeded, for example, bydamage to the ossicular chain or the ear canal. Individuals sufferingfrom conductive hearing loss can retain some form of residual hearingbecause some or all of the hair cells in the cochlea function normally.

Individuals suffering from conductive hearing loss often receive aconventional hearing aid. Such hearing aids rely on principles of airconduction to transmit acoustic signals to the cochlea. In particular, ahearing aid typically uses an arrangement positioned in the recipient'sear canal or on the outer ear to amplify a sound received by the outerear of the recipient. This amplified sound reaches the cochlea causingmotion of the perilymph and stimulation of the auditory nerve.

In contrast to conventional hearing aids, which rely primarily on theprinciples of air conduction, certain types of hearing prosthesescommonly referred to as bone conduction devices, convert a receivedsound into vibrations. The vibrations are transferred through the skullto the cochlea causing motion of the perilymph and stimulation of theauditory nerve, which results in the perception of the received sound.Bone conduction devices are suitable to treat a variety of types ofhearing loss and can be suitable for individuals who cannot derivesufficient benefit from conventional hearing aids.

SUMMARY

Aspects disclosed herein relate to medical devices having an implantableportion and an external portion. The implantable portion and externalportion each include a transmission/receiver coil that are used forsignal (data and/or power) transmission between the two portions. Theimplanted coil is disposed about or around the ear canal while theexternal coil is disposed about the pinna or in the ear canal itself.The proximity of the two coils allows for signal transmission. Incertain examples, configuration and location of the implantable andexternal coils can result in the elimination of magnets in theimplantable and external portions.

This summary is provided to introduce a selection of concepts in asimplified form that are further described below in the DetailedDescription. This summary is not intended to identify key features oressential features of the claimed subject matter, nor is it intended tobe used to limit the scope of the claimed subject matter.

BRIEF DESCRIPTION OF THE DRAWINGS

The same number represents the same element or same type of element inall drawings.

FIG. 1 is a partial view of an auditory prosthesis worn on a recipient.

FIGS. 2A and 2B are schematic top views of an implantable portion of anauditory prosthesis in accordance with an example of the proposedtechnology.

FIGS. 2C and 2D depict partial schematic views of a wire bundling systemin accordance with an example of the proposed technology.

FIG. 3 is a schematic top view of an implantable portion of an auditoryprosthesis in accordance with another example of the proposedtechnology.

FIGS. 4A and 4B are schematic top and section views of an implantableportion of an auditory prosthesis in accordance with another example ofthe proposed technology.

FIG. 4C depicts a partial enlarged schematic top view of the implantableportion of FIGS. 4A and 4B.

FIGS. 5A-5C are schematic side views of external portions of auditoryprostheses in accordance with examples of the proposed technology.

FIGS. 6A-6C depict examples of external portions of auditory prosthesesworn by a recipient.

FIGS. 7A-7C depict examples of auditory prostheses worn by a recipient.

FIG. 8 depicts a method of implanting an implantable portion of anauditory prosthesis.

DETAILED DESCRIPTION

The coil technologies disclosed herein can be used in conjunction withvarious types of auditory prostheses, including direct acoustic devicesand cochlear implants. Such devices include an implantable portion andan external portion. The implantable portion includes an implantablecoil disposed around or about the ear canal and provides a stimulus tothe recipient. The external portion receives sound, processes soundsignals, and sends signals to the implantable coil via an external coil.The external portions can be worn hung from the ear as a so-calledbehind-the-ear (“BTE”) device, or in the ear canal as a so-calledin-the-ear (“ITE”) device (like a traditional acoustic hearing aid).Devices that include a vibrating stimulator or a loud speaker are alsocontemplated, as are hybrid devices that include a number of differentstimulation systems. The corresponding stimulus can be in the form ofelectrical signals or mechanical actuations. For clarity, however, thetechnologies disclosed herein will be generally described in the contextof cochlear implants.

Referring to FIG. 1, cochlear implant system 10 includes an implantablecomponent 44 typically having an internal or implantablereceiver/transceiver unit 32, a stimulator unit 20, and an elongate lead18. The internal receiver/transceiver unit 32 permits the cochlearimplant system 10 to receive signals from (and/or transmit signals to)an external device 100. The internal receiver/transceiver unit 32includes an internal or implantable coil 36, and a magnet (not shown)fixed relative to the internal coil 36. The received signals generallycorrespond to external sound 13. Internal receiver unit 32 andstimulator unit 20 are hermetically sealed within a biocompatiblehousing, sometimes collectively referred to as a stimulator/receiverunit. The magnets facilitate the operational alignment of the externaland internal coils, enabling internal coil 36 to receive power andstimulation data from external coil 30. The external coil 30 iscontained within an external portion attached to a head of a recipient.Elongate lead 18 has a proximal end connected to stimulator unit 20, anda distal end implanted in cochlea 40. Elongate lead 18 extends fromstimulator unit 20 to cochlea 40 through mastoid bone 19.

In certain examples, external coil 30 transfers electrical signals(e.g., power and stimulation data) to internal coil 36 via a radiofrequency (RF) link, as noted above over a closely coupled inductivecoil link. Internal coil 36 is typically a wire coil comprised ofmultiple turns of electrically insulated single-strand or multi-strandplatinum or gold wire. The electrical insulation of internal coil 36 isprovided by a flexible silicone molding. Various types of energytransfer, such as electromagnetic, capacitive and inductive transfer,can be used to transfer the power and/or data from external device tocochlear implant. Several configurations of external and internal coilsare described in further detail herein.

There are a variety of types of intra-cochlear stimulating assembliesincluding short, straight and peri-modiolar. Stimulating assembly 46 isconfigured to adopt a curved configuration during and or afterimplantation into the recipient's cochlea 40. To achieve this, incertain arrangements, stimulating assembly 46 is pre-curved to the samegeneral curvature of a cochlea 40. Such examples of stimulating assembly46, are typically held straight by, for example, a stiffening stylet(not shown) or sheath which is removed during implantation, oralternatively varying material combinations or the use of shape memorymaterials, so that the stimulating assembly can adopt its curvedconfiguration when in the cochlea 40. Other methods of implantation, aswell as other stimulating assemblies which adopt a curved configuration,can be used.

Stimulating assembly can be a peri-modiolar, a straight, or a mid-scalaassembly. Alternatively, the stimulating assembly can be a shortelectrode implanted into at least in basal region. The stimulatingassembly can extend towards apical end of cochlea, referred to ascochlea apex. In certain circumstances, the stimulating assembly can beinserted into cochlea via a cochleostomy. In other circumstances, acochleostomy can be formed through round window, oval window, thepromontory, or through an apical turn of cochlea.

Speech processing components, such as microphones, speech processinghardware and software, and other elements, can be disposed within ahousing separate from the implantable portion of the auditoryprosthesis. In certain examples, such components can be contained in anexternal portion that also includes the external coil described above.In another example, the sound processing components can be containedwithin a BTE device, such as BTE 100 depicted in FIG. 1. In the lattercase, signals from the sound processing components are sent to anexternal portion containing the external coil.

FIGS. 2A and 2B are schematic top views of an implantable portion 200 ofan auditory prosthesis in accordance with an example of the proposedtechnology, and are described simultaneously. The implantable portion200 includes a housing 202 typically of silicone or other biocompatiblematerial. A stimulator unit 204 is disposed therein and generates astimulus (e.g., an electrical signal) to be delivered to the cochlea.The stimulator unit 204 is connected to one or more transmissionelements such as electrodes 206 a, 206 b that extend therefrom. Theelectrodes 206 a, 206 b are utilized to transmit or conduct theelectrical stimulus signals to the cochlea. As described above, cochlearimplants also typically include a coil and a magnet disposed in thehousing 202. In the depicted example, however, a flexible wire 208 thatfunctions as the coil is disposed outside the housing 202. In anexample, the wire 208 can be gold doped in calcium. Moreover, in certainexamples, a magnet need not be utilized. In a significant deviation fromknown systems, the flexible wire 208 is connected at a first end 210 tothe stimulator unit 204. As part of the implantation procedure, theimplantable portion 204 is implanted proximate the ear canal, as knownto persons of skill in the art. The flexible wire 208 is routed aboutthe ear canal C to form one or more loops 212 that, once the loops 212are completed, form a receiver coil 214. To ease implantation andguiding of the wire 208, a second end 216 can include a needle 218,which a surgeon can use to guide the wire 208 around the ear canal Cusing forceps or other instruments. Once the desired number of loops 212are made about the ear canal C, the needle 218 acts as a connector andis connectable to a port 220 in the stimulator unit 204 and the housing202. Once detachably received in the port 220, the completed implantablecoil 214 is formed. Any number of loops 212 can be made about the earcanal C, as required or desired for a particular application. In certainexamples, a greater number of loops 212 can be utilized to form a coil214 having greater quality of signal transmission/reception.

The examples depicted in FIGS. 2A and 2B depict loose loops 212 of thewire 208 that form the coil 214. However, it can be advantageous thatthe loops 212 are disposed close to each other so as to improve signaltransmission and reception. In that regard, FIGS. 2C and 2D depict awire bundling system 250 in accordance with an example of the proposedtechnology and are described simultaneously. A wire 208 is surrounded bya silicone or other resilient, flexible sheath or sleeve 252 thatelectrically insulates. Additionally, the sleeve 252 can be stretchableand the wire 208 can have a wave-like configuration so as to lengthen asthe sleeve 252 is stretched. The sleeve 252 includes a body 254 in whichthe wire 208 is disposed. Secured to or integral with the body 254 is aU-shaped bracket 256. The U-shaped bracket 256 defines a channel 258sized to receive the body 254 as it is looped during implantation.During implantation, a first loop about the ear canal C is made asdescribed above. Thereafter, an end of the body 254 is inserted into theU-shaped bracket 256 and advanced substantially parallel within an axisA of the channel 258 until a bundle 260 having the desired number ofclosely-disposed loops is formed. An interior surface of the U-shapedbracket 256 can be coated with a low-friction coating to ease slidinginsertion of the body 254 therein.

FIG. 3 is a schematic top view of an implantable portion 300 of anauditory prosthesis in accordance with another example of the proposedtechnology. A number of the elements are described above with regard toFIGS. 2A and 2B and are not necessarily described further. Theseelements are numbered consistently with those of FIGS. 2A and 2B, butbeginning with 300. Here, the wire 308 is configured in a helical shape,which can provide greater flexibility during implantation of the wire308, and can also improve signal transmission/reception quality. As withthe examples depicted elsewhere herein, one or more loops 312 about theear canal C can be made.

FIGS. 4A and 4B are schematic top and section views of an implantableportion 400 of an auditory prosthesis in accordance with another exampleof the proposed technology. FIGS. 4A and 4B are described simultaneouslyalong with FIG. 4C, which depicts a partial enlarged top view of theimplantable portion 400. A number of the elements are described abovewith regard to FIGS. 2A and 2B and are not necessarily describedfurther. These elements are numbered consistently with those of FIGS. 2Aand 2B, but beginning with 400. A first end 410 of a wire 408 isconnected to and extends from a stimulator unit 404 and makes a numberof turns or partial loops 412 in a generally circular pattern beforeterminating at a second end 416. This circular pattern of curved wire408 forms a substantially circular coil 414. At the second end 416, thewire 408 terminates at a connector 418 a. The loops 412 can optionallybe disposed within a flexible sleeve 418 which can be manufactured fromthe same material as the housing 402 (e.g., silicone) and in certainexamples is integral therewith. The sleeve 418 can be biased into apredefined orientation (e.g., curved) so it can more easily encircle theear canal C during implantation. A biasing element 422 can include awire or elastic element within or on the sleeve 418 that urges thesleeve 418 into a predefined configuration. Once disposed completelyaround the ear canal C, the connector 418 a can be inserted into amating port 420 in the housing 402 and connected to stimulator unit 404.A seal can be formed between the sleeve 418 and the port 420, e.g., witha friction fit, snap connector, adhesive, or combinations thereof. Onceconnected, the sleeve 418 forms an annulus with an open central portion.In another example, the wire 408 and sleeve 418 can be permanentlyconnected at the stimulator unit 404.

As described above, certain examples of implantable portions depictedherein do not utilize a magnet. This has significant advantages in thatthe implantable portion can still be worn by the recipient during amagnetic resonance imaging (MM) or other procedure that would typicallyrequire removal of the implantable portion and/or magnet. Typically,magnets in the implantable portion and in the external portion of theauditory prosthesis interact so as to hold the external portionproximate the implantable portion to ensure proper signal transmissionbetween the implantable coil and external coil. Absence of magnets,therefore, can cause signal transmission problems between theimplantable portion and the external portion. The disclosed technologiesaddress this and other problems by disposing the external transmissioncoil proximate the area of implantation of the implantable coil, andutilize body parts (e.g., the pinna or the ear canal) to ensure theimplantable and external coils remain proximate each other when theexternal portion is disposed in or proximate the head.

FIGS. 5A-5C are schematic side views of external portions 500 a-500 c ofauditory prostheses in accordance with examples of the proposedtechnology. In FIG. 5A, the auditory prosthesis 500 a includes a housing502 a, in this case in the form factor of a BTE device. The BTE device500 a includes a sound processor, microphones, batteries, and othercomponents described herein, which are not depicted in FIG. 5A. The BTEdevice 500 a includes a wire or lead 504 a extending therefrom. In thedepicted example, the wire 504 a is a twisted radio frequency (RF) coilthat adapts to the circumference of the pinna. The wire 504 a can bedisposed in a flexible (e.g., silicone) sleeve 506 a for comfort when incontact with the pinna of the recipient. The sleeve 506 a can besubstantially transparent or flesh-colored to disguise the appearancethereof. An oval shape can help further disguise the sleeve 506 a. Inother examples, circular, crescent, or other shapes can be utilized. Thewire 504 a can be configured to straighten within the silicone sleeve506 a, so as to more comfortably stretch to fit the recipient,regardless of pinna size. A portion 508 a of the wire 504 a is disposedwithin the housing 502 a, to form a complete coil 510 a. In FIG. 5B, anauditory prosthesis 500 b includes a housing 502 b and a wire 504 bhaving at least a portion 508 b disposed therein. The wire 504 bincludes a connector 512 b that connects a second end 514 b of the wire504 b to the housing 502 b, so as to form a complete coil 510 b. Asabove, the wire 504 b can be disposed within a silicon sleeve 506 a, ifrequired or desired. In this example, after the BTE device 500 b isplaced on the pinna, the wire 504 b and sleeve 506 b can be loopedaround the pinna and connected to the housing 502 b with a connector 512b, thus forming the coil 510 b. In FIG. 5C, an auditory prosthesis 500 cincludes a housing 502 c and a wire 504 c having at least a portion 508c disposed therein. The wire 504 c includes an elastic ring 516 c thatcan be used to tighten the coil 510 c around the pinna. As above, thewire 504 c can be disposed within a silicon sleeve 506 c.

FIGS. 6A-6C depict examples of external portions 600 a-600 c of auditoryprostheses worn by a recipient. In FIG. 6A, the auditory prosthesisincludes an external portion having a housing 602 a worn behind the ear(as a BTE device) and a coil 604 a disposed about the pinna. In FIG. 6B,the auditory prosthesis has a housing 602 b configured to fit within theear canal (as an ITE device). An external coil 604 b is connected to thehousing 602 b and extends around the pinna. In FIG. 6C, the housing 602c of the auditory prosthesis 600 c is configured to fit within the earcanal (again, as in an ITE device). The housing 602 c contains anexternal coil 604 c that communicates with an implantable coil 606 cdisposed about the ear canal, as described elsewhere herein. Theimplantable coil 606 c is connected to a stimulator unit 608 c, such asthose depicted above.

FIGS. 7A-7C depict examples of auditory prostheses 700 a-700 c worn by arecipient. The relative positions of the various components and the earcanal C are depicted and described in more detail herein. In FIG. 7A,the auditory prosthesis 700 a includes an external portion 702 a in theform of a BTE device housing 704 a. A coil 706 a sized to encircle thepinna is connected to the BTE device housing 704 a, for example in oneof the configurations depicted herein. An implantable portion 708 a is acochlear implant having a housing 710 a containing a stimulator unit. Acoil 712 a is disposed about the ear canal C. Given the proximity of thecoils 706 a, 712 a, signals can be communicated therebetween so as tocause a stimulus to be sent to a recipient of the auditory prosthesis700 a.

In FIG. 7B, the auditory prosthesis 700 b includes an external portion702 b in the form of a BTE device housing 704 b. Here, the BTE devicehousing 704 b is configured so as to be worn low on the pinna. This canbe desirable because it allows the BTE device housing 704 b to be atleast partially hidden by the ear lobe. Additionally, one or moremicrophones 714 b can be disposed on a forward-facing surface of the BTEdevice housing 704 b, which can improve sound reception. A coil 706 bsized to encircle the pinna is connected to the BTE device housing 704b, for example in one of the configurations depicted herein. Animplantable portion 708 b is a cochlear implant having a housing 710 bcontaining a stimulator unit. A coil 712 b is disposed about the earcanal C. Given the proximity of the coils 706 b, 712 b, signals can becommunicated therebetween so as to cause a stimulus to be sent to arecipient of the auditory prosthesis 700 b.

In FIG. 7C, the auditory prosthesis 700 c includes an external portion702 c in the form of a ITE device housing 704 c. Here, the ITE devicehousing 704 c is configured so as to be disposed within the ear canal(not shown here). A coil 706 c is disposed within the ITE device housing704 c, thus providing a very non-obtrusive option for recipient who maydesire the discretion of a more traditional hearing aid. An implantableportion 708 c is a cochlear implant having a housing 710 c containing astimulator unit. A coil 712 c is disposed about the ear canal. Given theproximity of the coils 706 c, 712 c, signals can be communicatedtherebetween so as to cause a stimulus to be sent to a recipient of theauditory prosthesis 700 c.

FIG. 8 depicts a method 800 of implanting an implantable portion of anauditory prosthesis. The method 800 begins at operation 802 where anincision is formed in the head of a recipient, proximate the pinna. Atoperation 804, an implantable portion of an auditory prosthesis isinserted into the incision. As described elsewhere herein, theimplantable portion can be a cochlear implant, direct acousticstimulator, or other implantable portion of an auditory prosthesis. Atoperation 806, a wire is implanted about the ear canal so as to form acoil. Operation 808 describes an example implantation of the wire whichcan include guiding an end of the wire about the ear canal. In decision810, it is determined if a desired number of loops are formed. If thedesired number of loops are not formed, flow returns to operation 808.If the desired number of loops have been formed, flow continues tooperation 812. Of course, certain examples of implantable devicesdescribed herein require only a single loop about the ear canal (e.g.,the sleeve and wire combination of FIGS. 4A and 4B). Once the desirednumber of loops are formed, operation 812 describes connecting the endof the wire to the implantable portion. The incision can then be closed.Other coil implantation processes are contemplated. For example, the earcanal can be severed or the pinna can be at least partially removed soas to ease implantation. In such an example, an implantable portionsimilar to the type depicted in FIGS. 4A-4C can be utilized. Such anexample would have a wire 408 and a sleeve 418 permanently connected atboth ends thereof to the stimulator unit 404. Once the ear canal and/orpinna have been severed, or partially removed, the annular sleeve 418can be placed around the ear canal, and then the severed/removed anatomycan be reattached.

This disclosure described some examples of the present technology withreference to the accompanying drawings, in which only some of thepossible examples were shown. Other aspects can, however, be embodied inmany different forms and should not be construed as limited to theexamples set forth herein. Rather, these examples were provided so thatthis disclosure was thorough and complete and fully conveyed the scopeof the possible examples to those skilled in the art.

Although specific aspects are described herein, the scope of thetechnology is not limited to those specific examples. One skilled in theart will recognize other examples or improvements that are within thescope of the present technology. Therefore, the specific structure,acts, or media are disclosed only as illustrative examples. The scope ofthe technology is defined by the following claims and any equivalentstherein.

What is claimed is:
 1. A system comprising: an implantable portionincluding: a housing; a stimulator unit disposed within the housing forgenerating a stimulus; a flexible sleeve connected to the housing; and awire disposed within the flexible sleeve, wherein the wire comprises aconnector disposed at an end of the wire; and at least one transmissionelement extending from the implantable portion for transmitting thestimulus, wherein the stimulator unit comprises a port for detachablyreceiving the connector; and wherein the flexible sleeve is configuredto be guidable into one or more loops during implantation of theflexible sleeve in a recipient to form a receiver coil.
 2. The system ofclaim 1, further comprising: an external portion including: an externalhousing disposed remote from the housing of the implantable portion; andan external coil configured to communicate with the wire when theexternal coil is disposed proximate a head of the recipient.
 3. Thesystem of claim 2, wherein the external housing comprises abehind-the-ear portion of an auditory prosthesis, and wherein theexternal coil is sized to be disposed about a pinna of the recipient. 4.The system of claim 2, wherein the external housing comprises anin-the-ear portion of an auditory prosthesis, and wherein the externalcoil is sized to be disposed about a pinna of the recipient.
 5. Thesystem of claim 2, wherein the external housing comprises an in-the-earportion of an auditory prosthesis, and wherein the external coil isdisposed within the in-the-ear portion.
 6. The system of claim 1,wherein the connector comprises a needle for connecting at least aportion of the wire to the housing.
 7. The system of claim 1, whereinthe flexible sleeve is biased into a curved configuration.
 8. The systemof claim 1, wherein the flexible sleeve defines a body in which the wireis disposed; wherein the system further comprises a bracket secured toor integral with the flexible sleeve; and wherein the bracket defines achannel configured to receive the body as the body is looped duringimplantation.
 9. The system of claim 1, wherein when the connector isreceived in the port, the flexible sleeve defines an annulus.
 10. Thesystem of claim 1, wherein the stimulator unit is configured to receivepower or data from the wire when the connector is received in the port.11. An apparatus comprising: an implantable housing including astimulator unit disposed within the implantable housing for generating astimulus; a flexible implantable wire extending from the implantablehousing and in communication with the stimulator unit, wherein theflexible implantable wire includes a first end connected to thestimulator unit and a second end connectable to the stimulator unit,wherein the flexible implantable wire is configured to send a signal tothe stimulator unit; and at least one transmission element extendingfrom the implantable housing for transmitting the stimulus generated bythe stimulator unit, wherein the implantable housing comprises a portfor receiving the second end; and wherein the flexible implantable wireis configured to be guidable into one or more loops during implantationof the flexible implantable wire in a recipient to form a receiver coil.12. The apparatus of claim 11, wherein the flexible implantable wire isconfigured to have a helical shape.
 13. The apparatus of claim 11,wherein the flexible implantable wire is embedded in a samebiocompatible material as a material that forms the implantable housing.14. The apparatus of claim 11, wherein the apparatus is a cochlearimplant and is characterized by an absence of a retention magnet. 15.The apparatus of claim 11, wherein the second end is a needle.
 16. Asystem comprising: an external portion of an auditory prosthesis, theexternal portion including: a sound processor; and an external coilconfigured to receive a sound processor signal from the sound processor;and an apparatus comprising: an implantable housing including astimulator unit disposed within the implantable housing for generating astimulus; a flexible implantable wire extending from the implantablehousing and in communication with the stimulator unit, wherein theflexible implantable wire includes a first end connected to thestimulator unit and a second end connectable to the stimulator unit,wherein the flexible implantable wire is configured to send a signal tothe stimulator unit; and at least one transmission element extendingfrom the implantable housing for transmitting the stimulus generated bythe stimulator unit, wherein the implantable housing comprises a portfor receiving the second end; and wherein the flexible implantable wireis configured to be guidable into one or more loops during implantationof the flexible implantable wire in a recipient to form a receiver coil.17. The system of claim 16, wherein both the sound processor and theexternal coil are disposed within the external portion.
 18. The systemof claim 16, wherein the sound processor is disposed within the externalportion and the external coil is connected at a first end to theexternal portion and connectable at a second end to the externalportion.
 19. The system of claim 18, wherein the external portioncomprises a behind-the-ear portion of the auditory prosthesis.
 20. Thesystem of claim 17, wherein the external portion comprises an in-the-earportion of the auditory prosthesis.